Micro-nano Fabrication Technology Research Articles

Efficient Second-Harmonic Generation in Adapted-Width Waveguides Based on Periodically Poled Thin-Film Lithium Niobate.

Frequency conversion process based on periodically poled thin-film lithium niobate (PPTFLN) has been widely recognized as an important component for quantum information and photonic signal processing. Benefiting from the tight confinement of optical modes, the normalized conversion efficiency (NCE) of nanophotonic waveguides is improved by orders of magnitude compared to their bulk counterparts. However, the power conversion efficiency of these devices is limited by inherent nanoscale inhomogeneity of thin-film lithium niobate (TFLN), leading to undesirable phase errors. In this paper, we theoretically present a novel approach to solve this problem. Based on dispersion engineering, we aim at adjusting the waveguide structure, making local waveguide width adjustment at positions of different thicknesses, thus eliminating the phase errors. The adapted waveguide width design is applied for etched and loaded waveguides based on PPTFLN, achieving the ultrahigh power conversion efficiency of second harmonic generation (SHG) up to 2.1 × 104%W-1 and 6936%W-1, respectively, which surpasses the power conversion efficiency of other related works. Our approach just needs standard periodic poling with a single period, significantly reducing the complexity of electrode fabrication and the difficulty of poling, and allows for the placing of multiple waveguides, without individual poling designs for each waveguide. With the advantages of simplicity, high production, and meeting current micro-nano fabrication technology, our work may open a new way for achieving highly efficient second-order nonlinear optical processes based on PPTFLN.

Laser-machined micro-supercapacitors: from microstructure engineering to smart integrated systems.

With the rapid development of portable and wearable electronic devices, there is an increasing demand for miniaturized and lightweight energy storage devices. Micro-supercapacitors (MSCs), as a kind of energy storage device with high power density, a fast charge/discharge rate, and a long service life, have attracted wide attention in the field of energy storage in recent years. The performance of MSCs is mainly related to the electrodes, so there is a need to explore more efficient methods to prepare electrodes for MSCs. The process is cumbersome and time-consuming using traditional fabrication methods, and the development of laser micro-nano technology provides an efficient, high-precision, low-cost, and convenient method for fabricating supercapacitor electrodes, which can achieve finer mask-less nanofabrication. This work reviews the basics of laser fabrication of MSCs, including the laser system, the structure of MSCs, and the performance evaluation of MSCs. The application of laser micro-nanofabrication technology to MSCs and the integration of MSCs are analyzed. Finally, the challenges and prospects for the development of laser micro-nano technology for manufacturing supercapacitors are summarized.

Orietation-controlled synthesis and Raman study of 2D SnTe

Tin telluride (SnTe), as a narrow bandgap semiconductor material, has great potential for developing photodetectors with wide spectra and ultra-fast response. At the same time, it is also an important topological crystal insulator material, with different topological surface states on several common surfaces. Here, we introduce different Sn sources and control the growth of regular SnTe nanosheets along the (100) and (111) planes through the atmospheric pressure chemical vapor deposition method. It has been proven through various characterizations that the synthesized SnTe is a high-quality single crystal. In addition, the angular resolved Raman spectra of SnTe nanosheets grown on different crystal planes are first demonstrated. The experimental results showed that square SnTe nanosheets grown along the (100) plane exhibit in-plane anisotropy. At the same time, we use micro-nanofabrication technology to manufacture SnTe-based field effect transistors and photodetectors to explore their electrical and optoelectronic properties. It has been confirmed that transistors based on grown SnTe nanosheets exhibit p-type semiconductor characteristics and have a high response to infrared light. This work provides a new approach for the controllable synthesis of SnTe and adds new content to the research of SnTe-based infrared detectors.

MXene Fibers for Flexible and Wearable Electronics: Recent Progress and Future Perspectives.

With the impetus of flexible electronics and micro-nano fabrication technology, the human demand for flexible intelligent wearable devices is on an upsurge. In recent years, new functional fibers have undergone rapid development and emerged as an indispensable carrier of flexible wearable e-textiles. However, to achieve their functional applications and durability, new functional fibers must possess good electrical and mechanical properties. As an emerging two-dimensional material, MXenes have attracted immense attention for their high electrical conductivity, mechanical strength, specific surface area, adjustable surface properties, and exceptional processability. As such, MXenes have become an ideal candidate for the primary functional component of functional fibers. This paper presents a comprehensive review of research progress on MXene-based fibers in the construction of flexible wearable electronic textiles. Firstly, we briefly outline the preparation methods of MXenes materials. Next, we summarize the processing types of MXene-based fibers and highlight their performance parameters. Lastly, we summarize the primary application scenarios of MXene-based fibers and anticipate the future development of flexible wearable e-textiles.

High-Precision and Rapid Direct Laser Writing Using a Liquid Two-Photon Polymerization Initiator.

Two-photon polymerization based direct laser writing (DLW) is an emerging micronano 3D fabrication technology wherein two-photon initiators (TPIs) are a key component in photoresists. Upon exposure to a femtosecond laser, TPIs can trigger the polymerization reaction, leading to the solidification of photoresists. In other words, TPIs directly determine the rate of polymerization, physicochemical properties of polymers, and even the photolithography feature size. However, they generally exhibit extremely poor solubility in photoresist systems, severely inhibiting their application in DLW. To break through this bottleneck, we propose a strategy to prepare TPIs as liquids via molecular design. The maximum weight fraction of the as-prepared liquid TPI in photoresist significantly increases to 2.0 wt %, which is several times higher than that of commercial 7-diethylamino-3-thenoylcoumarin (DETC). Meanwhile, this liquid TPI also exhibits an excellent absorption cross section (64 GM), allowing it to absorb femtosecond laser efficiently and generate abundant active species to initiate polymerization. Remarkably, the respective minimum feature sizes of line arrays and suspended lines are 47 and 20 nm, which are comparable to that of the-state-of-the-art electron beam lithography. Besides, the liquid TPI can be utilized to fabricate various high-quality 3D microstructures and manufacture large-area 2D devices at a considerable writing speed (1.045 m s-1). Therefore, the liquid TPI would be one of the promising initiators for micronano fabrication technology and pave the way for future development of DLW.

Flexible and Wearable Biosensors for Monitoring Health Conditions.

Flexible and wearable biosensors have received tremendous attention over the past decade owing to their great potential applications in the field of health and medicine. Wearable biosensors serve as an ideal platform for real-time and continuous health monitoring, which exhibit unique properties such as self-powered, lightweight, low cost, high flexibility, detection convenience, and great conformability. This review introduces the recent research progress in wearable biosensors. First of all, the biological fluids often detected by wearable biosensors are proposed. Then, the existing micro-nanofabrication technologies and basic characteristics of wearable biosensors are summarized. Then, their application manners and information processing are also highlighted in the paper. Massive cutting-edge research examples are introduced such as wearable physiological pressure sensors, wearable sweat sensors, and wearable self-powered biosensors. As a significant content, the detection mechanism of these sensors was detailed with examples to help readers understand this area. Finally, the current challenges and future perspectives are proposed to push this research area forward and expand practical applications in the future.

Design of compact dual-mode photoelectric modulator with high process tolerance based on vanadium dioxide.

Opto-electro modulators with nanometer-scale footprint are indispensable in integrated photonic electronic circuits. Due to weak light-matter interactions and limits of micro-nano fabrication technology, it is challenging to shrink a modulator to subwavelength size. In recent years, hybrid modulators based on surface plasmons have been proposed to solve this problem. Although the introduced high lossy surface plasmons provide large modulation depth, the polarization selectivity limits its application. Toward this end, in this paper, we present a design of an ultra-compact vanadium oxide (VO2)-based plasmonic waveguide modulator for both transverse electric (TE) and transverse magnetic (TM) modes. The device consists of two silicon tapers and a silicon waveguide embedded with a VO2 wedge. When electrical signals put on the device change the phase of VO2 from a metal to an insulator, the output optical signals along the waveguide are significantly modulated. For a 1.5 µm length modulator operating at 1.55 µm wavelength, the extinction ratio is 11.62 dB for the TE mode and 8.86 dB for the TM mode, while the insertion loss is 4.31 dB for the TE mode and 4.12 dB for the TM mode. Furthermore, the proposed design has excellent tolerance for fabrication process error, which greatly increases the yield rate of products and indicates a promotable application prospect.

Perovskite micro-nano lasers and on-chip integration

<p indent="0mm">With the rapid development of photonic technologies and micro-nano fabrication technologies, optoelectronic devices tend to be miniaturized and integrated. Photonic integrated circuits (PICs) can adress the bottleneck problems of electronic chips, such as high-power consumption and slow computing speed. Micro-nano lasers are an important part in PICs, and they are the key device to generate optical signals. Perovskites are direct band gap semiconductor materials with high exciton binding energy and low defect densities. Therefore, they have high photoluminescence quantum yield and can be used as gain materials for micro-nano lasers. In addition, perovskite materials also have advantages of low non-radiation recombination rate, low manufacturing cost, tunable bandgap width, solution treatment, and so on. Because of these advantages, perovskite materials have been widely used in micro-nano lasers and other fields. At present, researchers have developed a variety of micro-nano fabrication methods to fabricate perovskite micro-nano structures. A variety of perovskite micro-nano lasers have been obtained by using perovskite micro-nano structures under the pump of pulses or continuous lasers. In PICs, it is necessary to use optical waveguides to couple laser sources to other photonic devices to form a complete photonic circuit. This paper first summarizes the synthesis methods of perovskite materials, including spin coating methods, cooling crystallization methods, inversion crystallization methods, antisolvent crystallization methods, space limited methods, and gas phase epitaxial growth methods. Among these synthesis methods, spin coating methods are simple, but only polycrystalline perovskite materials can be prepared. Single crystal perovskites can be prepared by cooling crystallization methods, inversion crystallization methods, antisolvent crystallization methods, space limited methods, and gas phase epitaxial growth methods. Next, fabrication methods of perovskite micro-nano structures are introduced, including space limited synthetic growth methods, nano imprinting methods, focused ion beam etching methods, and electron beam exposure methods. Space limited synthetic growth methods and nano imprinting methods have no damage to perovskite materials. Electron beam exposure methods have small damage to perovskite materials, and focused ion beam etching methods cause great damage to perovskite materials. Then, perovskite micro-nano lasers, including out-plane emission lasers and in-plane emission lasers, are introduced. Out-plane emission lasers emit the laser towards the free space, and they are not favorite for on-chip integration. In-plane emission lasers emit the laser towards the in-plane space, and they are easy to be integrated with the waveguide. In addition, the combination of perovskites and metal structures is expected to reduce the size of the laser to subwavelength scales based on plasmonic effects. We also introduce the on-chip integration of perovskite micro-nano lasers, including tip manipulation methods, overlay alignment methods, and transfer printing methods. Tip manipulation and overlay alignment methods can damage perovskite materials. Transfer printing methods do not cause damage to perovskite materials. Finally, the development trends of perovskite materials and micro-nano lasers are discussed. Although perovskite micro-nano lasers have made great progress, there are still some problems to be addressed. For example, lead in perovskite materials is toxic, so it is necessary to develop lead-free perovskite materials. Perovskite materials have poor stability, and their stability should be improved. Moreover, the realization of electrically pumped micro-nano lasers and on-chip integration is also a great challenge.

Research progress in lithium niobate on insulator lasers

<p indent="0mm">Lithium niobate on insulator (LNOI) is considered one of the most competitive integrated photonics platforms due to the excellent optical properties of lithium niobate crystal and their compatibility with semiconductor micro/nano processing. Based on the continuous improvement of micro-nano fabrication technology, various transmission and control devices, such as low-loss waveguides and high-quality factor micro-cavities, showing better performance than traditional bulk materials devices, have been realized on LNOI. However, as an essential part of integrated photonics, the research of LNOI laser has made a breakthrough recently. Lithium niobate is an indirect bandgap material and thus tough for electroluminescence. It is a feasible and straightforward scheme to realize optically pumped laser based on rare-earth ion doping. This paper summarizes our research group’s recent research progress on realizing microdisk, microring, and single-mode lasers based on rare-earth-ion-doped LNOI and related works from other groups. We hope this review could benefit the related research on the active devices on LNOI.

On/Off Switching of Valley Topological Edge States in the Terahertz Region

Topological photonic devices provide a powerful platform to control the flow of light because their topologically protected edge states can be immune to backscattering and be robust to impurities, disorders, and defects. As one of the topological photonic systems, valley photonic crystals have attracted great attention because they can achieve a large bandgap and be easily combined with modern micro-nano fabrication technology. Terahertz photonic devices are of enormous interest in next-generation communications. Here, we design a valley photonic crystal consisting of a triangular lattice with three metal rod scatterers. By rotating the three metal rods in opposite directions to break the inversion symmetry, we achieve a bandgap width of up to 70% and observe the transport of the edge states in the terahertz region. By replacing part of the structure with phase change material VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , on/off switching of the terahertz photonic topological edge states is realized, and the attenuation can be also modeled by adjusting the size of the VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> region. The proposed regime has potential applications in sensing and 6G communications.

Using sugar as a mask material (SAAMM) in micro-nano fabrication: a high-performance, green and simple method

Sugar is a natural food and a common organic compound that widely exists in nature. Sugar features easy patterning, solubility in water, environmental friendliness, low cost, and easy combination with micro-nano process. In this study, sugar is proposed to be used as a micro-nano mask material in micro-nano fabrication. Results show that sugar can be easily used to fabricate various kinds of micro-nano mask patterns on different wettability substrates. The fabrication method based on sugar mask has many advantages; it is diverse, simple, pollution-free, and inexpensive. Besides, sugar is strongly compatible with micro-nano fabrication technology, because it can maintain good peeling properties, good viscosity, and good stability in subsequent micro-nano fabrication and achieve the high-quality transfer of mask patterns. In addition, graphite super-lubricity micro-nano movable devices are made through the proposed sugar mask method, which also has good and reliable performance compared with e-beam lithography. Compared with micro-nano fabrication based on photoresist masks, micro-nano fabrication based on the sugar mask is simpler and cheaper. In the micro-nano processing of the sugar mask, the lift-off and removal of residual sugar can be easily completed using water. In summary, we believe that sugar as a mask material is effective and can be widely used in micro-nano manufacturing.

Controlling the Surface Roughness of Surface-Electrode Ion Trap Based on Micro-Nano Fabrication

The surface-electrode ion trap is one of the most promising devices to realize large-scale and integrated quantum information processing. However, a series of problems are faced in the micro-nano fabrication of surface-electrode ion traps. A prominent one is the difficulty to control the thick film surface roughness. A rough electrode surface could produce excessive radio frequency (RF) loss and deteriorate trapping ability of the surface-electrode ion trap. In this paper, a thick film micro-nano fabrication technology to control the surface roughness is presented, which can reduce the roughness of thick film surface-electrode down to 6.2 nm, while being controllable between 6.2 nm and 45 nm. Therefore, it can also provide a basis for studying the influence of electrode surface roughness on trap performance. The micro-nano fabrication technology is not only suitable for surface-electrode ion traps with various configurations, but also be further applied to researches of MEMS, solar cells and surface science.

Fabrication and application of flexible AlN piezoelectric film

A fabrication method for high quality flexible aluminum nitride piezoelectric thin films based on micro-nano fabrication technology is reported in this paper. Molybdenum (Mo)/aluminum nitride (AlN)/aluminum (Al) structure was prepared on silicon(100) by sputtering. Then, deep-reactive ion etching technology was used to remove the silicon material used for support, then the Mo/AlN/Al flexible sandwich film was obtained. The full-width at half-maximum of the AlN film (002) peak before and after removal of silicon was only 1.47° and 1.49°, respectively. No obvious cracks in the film under bending conditions were observed with a scanning electron microscope. Capacitance–voltage (C–V) test results showed that the capacitance curve of the sandwich structure was consistent with that of the double-sided Schottky junction. The flexible piezoelectric film with an active area of 2 × 2 mm2 exhibited an average peak-to-peak generated voltage of 0.6 V in energy harvesting tests, which indicates that the method could be used to fabricate high quality flexible energy collectors based on AlN film. The preparation scheme in this paper is compatible with integrated circuit processes and simple to implement, which lays a foundation for the wide application of flexible piezoelectric devices.

Research progress of photonics devices on lithium-niobate-on-insulator thin films

&lt;sec&gt; Lithium niobate (LiNbO&lt;sub&gt;3&lt;/sub&gt;, LN) crystals have excellent electro-optical and nonlinear optical properties, and they have been regarded as one of the most promising materials for constructing the multifunctional photonic integrated systems. Due to the excellent optical properties of LN crystal, the emerging LN thin film technology has received great attention in the research of integrated photonics in recent years. With the help of advanced micro-nano fabrication technologies, many high-performance lithium niobate integrated photonic devices have been realized. &lt;/sec&gt;&lt;sec&gt; Integrated photonic platform can incorporate high-density, multi-functional optical components, micro-nano photonics structures, and optical materials on a monolithic substrate, which can flexibly implement a variety of photonic functions. At the same time, it also provides a low-cost, small-size, and scalable solution for miniaturizing and integrating the free-space optical systems. Photonic chips based on LN have been widely used in fast electro-optic modulation, nonlinear optical frequency conversion and frequency comb generation. In particular, periodically poled lithium niobate (PPLN) based on quasi-phase matching has gradually become a mature integrated photonic platform and has been widely used in the field of nonlinear optics.&lt;/sec&gt;&lt;sec&gt; As wafer bonding technology is matured, the lithium-niobate-on-insulator (LNOI) thin films made by the “smart-cut” process have been commercialized. The thickness of the LN film on a Si or SiO&lt;sub&gt;2&lt;/sub&gt; substrate can reach several hundred nanometers, and good uniformity in film thickness at a larger size (3 inches) can be ensured. With the development of micro-nano fabrication technologies, the quality and functions of photonic devices on LNOI chips have been significantly improved in recent years, and research on integrated photonic devices based on LNOI has also been developed rapidly in recent years.&lt;/sec&gt;&lt;sec&gt; In this article we briefly review the development of LNOI technology, introducing the applications of several advanced micro-nano fabrication techniques and summarizing their applications in the micro-/nano-fabrication of on-chip photonic devices based on LNOI wafers. In addition, in this article we also summarize the latest advances in the functionality of LNOI on-chip photonic devices and give a short prospective on their future applications in integrated photonics.&lt;/sec&gt;

Laser Fabrication of Graphene-Based Flexible Electronics.

Recent years have witnessed the rise of graphene and its applications in various electronic devices. Specifically, featuring excellent flexibility, transparency, conductivity, and mechanical robustness, graphene has emerged as a versatile material for flexible electronics. In the past decade, facilitated by various laser processing technologies, including the laser-treatment-induced photoreduction of graphene oxides, flexible patterning, hierarchical structuring, heteroatom doping, controllable thinning, etching, and shock of graphene, along with laser-induced graphene on polyimide, graphene has found broad applications in a wide range of electronic devices, such as power generators, supercapacitors, optoelectronic devices, sensors, and actuators. Here, the recent advancements in the laser fabrication of graphene-based flexible electronic devices are comprehensively summarized. The various laser fabrication technologies that have been employed for the preparation, processing, and modification of graphene and its derivatives are reviewed. A thorough overview of typical laser-enabled flexible electronic devices that are based on various graphene sources is presented. With the rapid progress that has been made in the research on graphene preparation methodologies and laser micronanofabrication technologies, graphene-based electronics may soon undergo fast development.

Superior MoS2-decorated CNT composite materials for photoelectric detectors

Carbon nanotubes (CNTs), outstanding flexible and photoelectric materials, have inspired tremendous innovations in the fields of stretchable and wearable electronics. Exquisite optoelectronic materials are decorated on carbon nanotube walls is an universal method under modification process for CNT. This modification promotes the light-matter interactions and efficient charge-transfer pathways. In this respect, it is still challenging to prepare excellent CNT composites and fabricate state-of-the-art carbon-based flexible electronic devices effectly. Herein, we designed a MoS2-decorated CNT photoelectric composite materials by a facile self-assembly method, which realized exact compatibility and ingenious connection of CNT and MoS2. The flexible photoelectric electronic devices were fabricated by micro-nanofabrication technologies. The photocurrent of CNT-MoS2 exhibited 4 times higher than pure CNT materials, which showed superior photoresponse and recovery ability. The photoinduced charge transfer theory proved that the MoS2 is exceedingly good optical gain materials and benefiting from the interfacial charge-transfer transition. Therefore, the MoS2 can serve as a complement in applications that require excellent photovoltaic semiconductors, which has potential for obstaining the novel proporties nanomaterial system. The enhancement of photosensing performance showing the broad prospect of the burgeoning high performance wearable sensors.

Thermal Bubble Nucleation in a Nanochannel: An Experiment Investigation

We investigated the nanoscale thermal bubble nucleation based on the principle of Coulter counter. With micro-nanofabrication technologies, a device was designed and fabricated, and a detection platform was set up which was used to investigate the thermal bubble nucleation of aqueous solution confined in a nanochannel with a cross size of about 100 nm×100 nm. Results show that with the temperature of the solution confined in the nanochannel increasing, the current through the channel increases first and then decreases, and vanishes after a fluctuating period. It can be found that the generating thermal bubbles can hinder the current flowing through the nanochannel. In addition, the shrinking and expanding of thermal bubbles’ volume correspond to the increase and decrease of the current. Finally, the thermal bubbles block the nanochannel entirely. Through the experiment results, our device can be applied to investigate the complex behaviors of thermal bubble produced in aqueous solution confined in nanochannels, effectively.

Femtosecond Laser Micro-Nanofabrication Technology and its Experimental System

In this paper,a 3D femtosecond laser micro-nanofabrication system has been built. CAD model of 2D picture conversion data based on femtosecond laser micro-nanofabrication system have been also discussed. At last, the 2D hand model has been fabricated using the fabrication system we have built.

Lab‐on‐a‐Print: Desktop Microfabrication for Quantitative Biology

Motivated by the growing demand for low‐cost, easy‐to‐use, compact‐size yet powerful micro‐nanofabrication technologies, we have been investigating engineering solutions to address emerging challenges of fundamental biology and translational medicine in regular laboratory settings. Recent advancements in the field benefit considerably from rapidly expanding material selections, ranging from inorganics to organics and from nanoparticles to self‐assembled molecules. Meanwhile a great number of novel methodologies, employing off‐the‐shelf consumer electronics, intriguing interfacial phenomena, bottom‐up self‐assembly principles, etc., have been implemented to transit micro‐nanofabrication from a cleanroom environment to a desktop setup. Furthermore, the latest application of micro‐nanofabrication to emerging biomedical research will be presented, which includes point‐of‐care diagnostics, on‐chip cell culture as well as bio‐manipulation.

Whispering-gallery-mode microdisk lasers produced by femtosecond laser direct writing

We report in this Letter fabrication of whispering-gallery-mode microdisk lasers by femtosecond laser direct writing of dye-doped resins. Not only is well-defined disk shape upheld on an inverted cone-shaped supporter, but the disk also exhibits significant lasing actions characteristic of an abrupt increase of light output and the significant narrowing of the spectral lines when the threshold is approached. This work shows that the laser micronanofabrication technology is not only applicable to passive micro-optical components, but also it may play an important role in fabrication of active optoelectronic devices and their integrated photonic circuits.